Many studies reported in the literature have investigated the oxidation behavior of lipids in freeze dried emulsions without consideration for the physical structure of the dehydrated emulsion, and its influence on mass transport of oxygen to the lipid. Of particular importance is the air-lipid interfacial area, which can be influenced by lipid droplet size distribution and possible droplet inclusion in the matrix to give a barrier to oxygen transport. A number of process variables such as matrix solid, mixing conditions, freezing rate and drying conditions will influence the resultant air-lipid contact, as will storage conditions which result in alteration of matrix structure. The proposed work will investigate the role of emulsion physical structure on oxidation behavior of the lipid phase, with the aim to better understand the oxidative degradation behavior of dehydrated emulsified foods, and to aid in design of food systems which are more stable with respect to lipid oxidation. Studies undertaken to date have concentrated on developing chemical and microscopic techniques for evaluating matrix structure and quantifying the degree to which emulsion lipid is either incorporated into the freeze dried matrix, or present on the surface of the matrix. By these techniques, surface lipid can be quantitatively extracted while leaving the matrix structure unaltered. The efficiency of this selective extraction is checked with a lipid selective staining procedure and microscopic observations. Major differences of lipid-matrix interactions have been noted for freeze dried systems based on microcystalline cellulose or maltodextrin, primarily with respect to incorporation of lipid in the matrix. The extent of incorporation of lipid in maltodextrin matrices has also been shown to vary with freezing rate. BIBLIOGRAPHIC REFERENCES: Gejl-Hansen, F. and J. M. Flink Application of Microscopic Techniques to the Description of Structure of Dehydrated Food Systems J. Fd. Sci. (in press).